When it comes to big decisions, they do not come bigger than awarding a penalty kick.
A referee cannot guess. That unfortunately appears to have resulted in Leicester City's undoing in the Champions League.
They are 1-0 down after the first leg of their quarter final with Atletico Madrid as a result of a poor decision. This is the very type of call that can be resolved by the introduction of the Video Assistant Referee.
Last week in the A League in Australia the system in use came to the rescue of a referee who was able to clarify an incident with the VAR and point to the mark.
Referee Jonas Eriksson is one of UEFA's top operators so it is disappointing that he appeared to make a guess on this occasion and got it spectacularly wrong.
Where were his colleagues who should have been in a position to offer advice? I wonder how much consultation took place, before the point to the penalty mark. We have the assistant referee who can quickly recover position and look along that outer edge of the penalty area line to determine whether any offence is inside or out.
The additional official on the same side as the assistant can look down the penalty area line parallel to the touchline.
However, when calls are close to the line on the referee's diagonal he is expected to get into the correct position and to NOT guess.
On this occasion he was not ideally placed and sadly this big call could cost Leicester City. Top referees are human too and even the best will make mistakes so the sooner the VAR is introduced the better.